Field of the Invention
The present invention relates to a method for receiving control information through an enhanced physical downlink control channel (EPDCCH).
Related Art
3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) that is an advancement of UMTS (Universal Mobile Telecommunication System) is being introduced with 3GPP release 8. In 3GPP LTE, OFDMA (orthogonal frequency division multiple access) is used for downlink, and SC-FDMA (single carrier-frequency division multiple access) is used for uplink. The 3GPP LTE adopts MIMO (multiple input multiple output) having maximum four antennas. Recently, a discussion of 3GPP LTE-A (LTE-Advanced) which is the evolution of the 3GPP LTE is in progress.
As set forth in 3GPP TS 36.211 V10.4.0, the physical channels in 3GPP LTE may be classified into data channels such as PDSCH (physical downlink shared channel) and PUSCH (physical uplink shared channel) and control channels such as PDCCH (physical downlink control channel), PCFICH (physical control format indicator channel), PHICH (physical hybrid-ARQ indicator channel) and PUCCH (physical uplink control channel).
The PDCCH is used to transmit control information to a terminal. However, with diversification of control information and an increase in control information quantity, use of only existing PDCCHs reduces flexibility in scheduling. Thus, an enhanced PDCCH (EPDCCH) is adopted in LTE-A.
A base station transmits a demodulation reference signal (DMRS) so that a terminal demodulates an EPDCCH.
However, in recent years, as a significantly low signal-to-interference-plus-noise ratio (SINR, for example, 20 dB lower than in a normal situation) is requested or a terminal travels at very high speed, it is necessary to flexibly change a DMRS pattern.
When a DMRS pattern is changed, however, technical ambiguity in an EPDCCH between a terminal and a serving cell occurs and an imbalance between resource elements including a DMRS is caused.